It’s been nine years since his five-set U.S. Open finals classic against Roger Federer, but it’s a match Juan Martin del Potro will always remember in detail — right to the trophy presentation.

“I couldn’t hold the trophy in that moment,’’ the third-seeded del Potro recalled. “I was so nervous — happy. I couldn’t talk to the fans in that moment. But I have my trophy at home. I like to see that trophy every single day in my home. I don’t know if I can get a new one, but I’m doing all my best to try to get again.’’

After that 2009 gem, the 6-foot-6 Argentine baseliner with the piercing forehand was destined to collect a bunch of Open titles. Beset by a string of wrist surgeries, del Potro hasn’t won a single Grand Slam title since.

This may be his best chance — even though his opponent for Friday’s 4 p.m. semifinal is No. 1 seed and defending Open champion Rafael Nadal, followed by No. 21 Kei Nishikori of Japan facing No. 6 Novak Djokovic in a rematch of their 2014 semifinal.

This is the 17th clash for Nadal-del Potro — two sturdy baseliners. It’s also, incredibly, their fourth meeting in the past five Grand Slam events.

Though Nadal has beaten del Potro in all three of those matches, including last year’s Open semifinals, there’s a growing sense the Argentine has a big chance. Nadal can’t feel too spry after playing past 2 a.m. Wednesday to oust Dominic Thiem in a five-set quarterfinal.

To no surprise, Nadal took out del Potro in his clay castle at the French Open in a straight-set semifinal. But in the quarterfinals at Wimbledon in July, Nadal barely survived a wondrous five-setter.

“Yeah, will be a very tough,’’ Nadal said. “In Wimbledon he was a great player. He’s a great player on grass. He’s a great player everywhere. But the challenge of playing him on hard[court] is even higher for me personally than playing against him on clay. It will be a big challenge is a match we know each other very well. I know he’s playing well.”

Del Potro expects Friday’s match to be “as big a battle as Wimbledon.’’ If Nadal wins the Open, it will give him 18 slams and stir talk of catching Roger Federer (20) and stealing the mantle of greatest ever.

“I like to play always with the No. 1 of the world,’’ del Potro said. “I just have the chance to play the greatest on this sport and it’s amazing for me.’’

Del Potro, who will turn 30 in two weeks, may be playing his best tennis ever, adding a sliced backhand to offset his wrist pain. He ousted Federer in last year’s Open quarterfinals.

Novak DjokovicGetty Images

In this year’s quarterfinals, del Potro ousted American John Isner in a taut four-setter. Tennis Channel’s Justin Gimelstob, Isner’s coach, said he expects “an epic battle’’ and chess match.

“Rafa will use his favorite lefty patterns liberally, challenging del Potro’s backhand, which has become reliable,’’ Gimelstob said. “Del Potro has two of the biggest weapons in the sport — forehand and serve. He has the belief he can beat the best in the biggest moments and the slower courts suit him. But if anyone can regroup from a five-set marathon, it’s Rafa.’’

With Marin Cilic also turning 30 this month, there won’t a Grand Slam men’s champion in his 20’s. The Open wasn’t the breakthrough for the so-called “NextGen.’’ The men’s final four are familiar faces — Nishikori made the Open finals in 2014.

Djokovic entered as tournament favorite vying for his third Open title. He missed last year’s Open with elbow pain and underwent elbow surgery in February after a lousy performance at the Australian Open. Djokovic is all the way back and Nishikori probably is in over his head against the reigning Wimbledon champion.

“I don’t have a great record against Novak,’’ Nishikori said, referring to his 2-14 mark. “He doesn’t have many weaknesses.’’